Synthesis of molybdenum and tungsten carbonyls



Patented May 22, 1951 SYNTHESIS OF MOLYBDENUM AND TUNGSTEN CARBONYLSDallas '1. Hurd, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York No Drawing. Application June 6, 1950,Serial No. 166,551

Claims. (Cl. 23-203) The present invention relates to the synthesis ofcarbonyls of tungsten and molybdenum.

In accordance with a known method of preparing the carbonyl compounds ofthe heavier sixth group metals, molybdenum and tungsten, a chloride ofthe meta1 is reacted with carbon monoxide under pressure in the presenceof a reducing metal. The reducing metals which have been employedheretofore for this purpose are zinc dust and iron dust, zinc dust beingpreferred for better yields.

The present invention is based on the discovery that certain new andunexpected improvements can be obtained by substituting granularaluminum for the known reducing metals, such as zinc dust. It has beenfound that finely-divided aluminum consistently gives higher over-allyields of the desired carbonyl than will zinc under reaction conditionswhich are otherwise similar. In addition, the reaction forming thecarbonyl appears to proceed more rapidly with aluminum than with zinc oriron dust. A further advantage of the present invention is that thereaction mixtures employing aluminum are much easier to treat for theisolation of the carbonyl product than are those residues obtainedemploying zinc, for example, as the active metal. From the coststandpoint, aluminum is also preferable to zinc.

While in some cases the presence of a small amount of zinc dust may befound desirable for the purpose of initiating the carbonyl reaction, itis not essential for the actual reduction reaction and aluminum can beemployed without it.

The term aluminum reducing agen as used herein is intended to includeboth metallic aluminum and aluminum-rich alloys. An example of asuitable alloy is one containing 50% copper, 45% aluminum and 5% zinc.

In order that those skilled in the art better may understand how thepresent invention can be carried into effect, the following illustrativeexamples are given.

Example 1.--Employing a closed reactor, grams of tungsten hexachloridewas reacted with 30 grams of 40-mesh zinc powder in 100 milliliters ofanhydrous ether in the presence of 2500 lbs. per sq. in. of carbonmonoxide for 16 hours at about 20 C. The product isolated by steamdistillation of the reaction mixture comprised 3.6 grams of tungstenhexacarbonyl, representing a yield of approximately 41%.

Example 2.Example 1 was repeated employing grams of 30-mesh aluminum inplace of the 30 grams of 40-mesh zinc powder. In addition, the pressureof carbon monoxide was lower,

being only 1500 lbs. per sq. in. The product from this reactioncomprised 4.4 grams of tungsten hexacarbonyl, representing a yield ofabout 50%.

Example 3.-Example 1 was repeated substituting 15 grams of a powderedalloy of 50% copper, 45% aluminum and 5% zinc for the straight zinc. Theyield was 5.3 grams of tungsten carbonyl, representing a yield of aboutof the theoretical.

Example 4.-Employing a pressure reactor, 10 grams of tungstenhexachloride was reacted with 20 grams of -mesh zinc powder inmilliliters of ether under a pressure of 1500 lbs. per sq. in. carbonmonoxide for 16 hours at 70 C. The yield of the reaction was 1.9 gramsof tungsten carbonyl or about 21% of the theoretical.

Example 5.Example 4 was repeated, substituting 15 grams of 60-meshaluminum powder for the zinc powder and the reaction was carried out atroom temperature. The yield was 5.7 grams of tungsten carbonyl or ayield of about 64% of the theoretical.

Example 6.-Example 4 was repeated employing the copper-aluminum-zincalloy of Example 3 in place of the zinc. 15 grams of the powdered alloywas used. The reaction was carried out at a temperature of 100 for 3hours and yielded 8 grams of tungsten carbonyl, representing a yield ofabout 90%.

Example 7.Example 6 was repeated while maintaining the reaction at roomtemperature. The yield was 4.3 grams of tungsten carbonyl or about 49%of the theoretical.

Example 8.Examp1e 7 was repeated except that the pressure of carbonmonoxide was 2500 lbs. per sq. in. instead of 1500 lbs. per sq. in. Ayield of 4.7 grams of tungsten carbonyl represented about 53% of thetheoretical.

From the above examples, it will be seen that aluminum and aluminumalloys consistently give better yields of the tungsten carbonyl thandoes the zinc. This is particularly true at the higher reactiontemperatures of from 70 to C. In this respect, the use of elevatedtemperatures is directly contrary to the general teachings of the priorart regarding the preparation of carbonyls employing reducing metals.While the amount of aluminum present in the reaction mixture has beenfound to have only a slight effect on the yield of the reaction providedthat an amount sufficient to reduce the tungsten chloride is present, ingeneral, the amount of aluminum by weight should ordinarily equal orexceed the weight of the tungsten or molybdenum hexachloride beingreduced.

Molybdenum chloride can be substituted for tungsten chloride in any ofthe above examples with comparable results. With either molybdenum ortungsten chlorides, the reaction temperatures can range anywhere fromroom temperature to a maximum temperature of approximately 150 C. withtemperatures somewhat above room temperature being preferred.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A process of preparing a metalcarbonyl which comprises effectingreaction between carwhich comprises reacting tungsten chloride withcarbon monoxide under pressure and in the presence of aluminum.

5. The process of preparing tungsten carbonyl which comprises reactingtungsten chloride with carbon monoxideunder pressure and inthe presenceof a substantial quantity of finely divided aluminum admixed with saidchloride.

DALLAS T. HURD.

REFERENCES CITED The following references are of record in the file'ofthis patent:

UNITED STATES PATENTS Number Name Date 1,894,239 Naumann et al. Jan. 10,1933 1,944,849 Schlecht et al. Jan. 23, 1934 OTHER REFERENCES Mond: TheMetal Carbonyls, pages 276T and 277T. Jour. of the Society of ChemicalIndustry, vol. 49, No.24 (June 13, 1930).

1. A PROCESS OF PREPARING A METAL CARBONYL WHICH COMPRISES EFFECTINGREACTION BETWEEN CARBON MONOXIDE AND A HALIDE OF A METAL SELECTED FROMTHE GROUP CONSISTING OF TUNGSTEN AMD MOLYBDENUM IN THE PRESENCE OF ANALUMINUM REDUCING AGENT.